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234.java
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234.java
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__________________________________________________________________________________________________
sample 0 ms submission
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isPalindrome(ListNode head) {
int count=0;
ListNode it=head;
while(it!=null){count++;it=it.next;}
int[] vals=new int[count/2];
it=head;
for(int i=0;i<vals.length;i++){
vals[i]=it.val;
it=it.next;
}
if(vals.length>0 && count%2>0)it=it.next;
for(int i=vals.length-1;i>=0;i--){
if(vals[i]!=it.val) return false;
it=it.next;
}
return true;
}
}
__________________________________________________________________________________________________
sample 38440 kb submission
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isPalindrome(ListNode head) {
// Reverse the linked list and verify
ListNode fast = head;
ListNode slow = head;
Stack<Integer> stack = new Stack<Integer>();
// Push elements from first half of linked list onto stack. When fast
// runner reaches the end of the linked list, then we know we're at the
// middle
while (fast != null && fast.next != null) {
stack.push(slow.val);
slow = slow.next;
fast = fast.next.next;
}
if (fast != null) {
slow = slow.next;
}
while (slow != null) {
int top = stack.pop().intValue();
if (top != slow.val) {
return false;
}
slow = slow.next;
}
return true;
}
}
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